In a ball screw device which is used in a machine tool or a construction machine, a metal material having high hardness, such as high carbon chromium bearing steel, stainless steel, or case hardening steel, has been generally employed. However, in recent years, weight reduction has been strongly required, and by changing a screw shaft, which takes most part of the weight among members which configure the ball screw device, from the above-described steel material to fiber reinforced plastic (FRP), the weight reduction is achieved.
For example, Patent Document 1 describes that a filament bundle including organic fibers is wound by helical winding or parallel winding while being impregnated with a liquid thermosetting resin around a core made of aluminum or iron, is thermally cured, and is made into a columnar body, and then, is cut into a shape of the screw shaft.
In addition, Patent Document 2 describes a motion guide device in which the vicinity of a rolling body rolling surface consists of a metal material and other parts consist of FRP.
Furthermore, Patent Document 3 describes that, in a motion guide device which is used in a mechanical device which handles an X-ray, a lifespan is improved by using FRP which is an X-ray transmitting material in at least one of a track member, a moving member, and a rolling body, and by making a steel tape stick to a rolling body rolling surface.